projecteuler.net/057/main.rs

struct D {
    a: u32,
    b: u32
}

impl D {
    pub fn from(a: u32, b: u32) -> D {
        D { a: a, b: b }
    }
    pub fn print(&self) {
        println!("{}/{}", self.a, self.b);
    }
    pub fn add_n(&self, n: u32) -> D {
        let aa = self.b;
        return D::from(aa + self.a, self.b);
    }
    pub fn iter(&self) -> D {
        let mut res = self.add_n(1);
        let dd = D::from(res.b, res.a);
        return dd.add_n(1);
    }
}


fn main() {
    let mut d = D::from(1, 2);
    d = d.add_n(1);
    d.print();
    for n in 0..100 {
        d = d.iter();
        d.print();
    }
}